The present invention relates to devices of the type employed for controlling the vapor venting of motor vehicle fuel tanks during filling and also to provide emergency vent closure in the event of a vehicle rollover. Heretofore, it has been the practice to provide either a vent tube to the filler neck for the tank for venting during filling, in conjunction with a second vent to the vapor collecting canister employed for storage of fuel vapor during periods of engine inoperation and which is purged during engine operation.
Alternatively, the fill vent has also been connected to the canister in more recent vehicle applications. Where a float operated valve is employed to close the fill vent and the vent to the vapor canister, it is necessary to provide a pressure relief valve in the event the vapor pressure in the tank exceeds a predetermined incipient tank rupture threshold to a safety hazard of tank rupture. Heretofore, it has been common practice to provide individual valves for these functions, which has necessitated a plurality of openings in the fuel tank to provide access for each of the valves and vent port arrangements. Recently however, it has been found desirable to combine the various vent and valve functions in a commonly housed unit which can be inserted through a single access opening in the fuel tank to eliminate the need for separate sealing arrangements about the individual openings and thus simplify assembly of the tank and improve seal reliability.
The problem of providing such a commonly housed multiple vent and valve assembly for installation and sealing in a single access opening of a fuel tank is further compounded by the fact that many of the present day vehicle production fuel tanks are molded of plastic or polymeric material which is not compatible with the materials employed for the valve construction and which are capable of withstanding the vibration and impact loading requirements set for vehicle crash safety. Thus, it has been found difficult to provide such a commonly housed assembly for performing the various vent, pressure relief and fill vent shutoff functions which can readily be installed in a single tank access opening and sealed thereabout and accommodate various tank configurations and provide reliability in service.
However, in order to provide a combination vent and plural valve functions in a common unit inserted through a single tank opening, it has been necessary to provide a plurality of different valve housing configurations and float arrangements to accommodate the various tank configurations having different tank depth and fill level. This has necessitated a customized valve arrangement for each different tank configuration in which the valve must then be calibrated for the appropriate liquid shutoff level for the particular tank.
Thus, it has been desired to provide some way or means of having a common tank vent and fill valve shutoff valve which is low in manufacturing cost, and may be easily assembled in tanks of different configuration and capacities in a manner which enables the common valve to accommodate the different tank depths.